<template>
  <canvas id="canvas"></canvas>
</template>
<script>

export default {
  name: "diamond",
  mounted() {
    "use strict";

    var canvas = document.getElementById('canvas'),
        ctx = canvas.getContext('2d'),
        w = canvas.width = window.innerWidth,
        h = canvas.height = window.innerHeight,

        hue = 217,
        stars = [],
        count = 0,
        maxStars = 1400;

    var canvas2 = document.createElement('canvas'),
        ctx2 = canvas2.getContext('2d');
    canvas2.width = 100;
    canvas2.height = 100;
    var half = canvas2.width/2,
        gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);
    gradient2.addColorStop(0.025, '#fff');
    gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)');
    gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)');
    gradient2.addColorStop(1, 'transparent');

    ctx2.fillStyle = gradient2;
    ctx2.beginPath();
    ctx2.arc(half, half, half, 0, Math.PI * 2);
    ctx2.fill();

    // End cache

    function random(min, max) {
      if (arguments.length < 2) {
        max = min;
        min = 0;
      }

      if (min > max) {
        var hold = max;
        max = min;
        min = hold;
      }

      return Math.floor(Math.random() * (max - min + 1)) + min;
    }

    function maxOrbit(x,y) {
      var max = Math.max(x,y),
          diameter = Math.round(Math.sqrt(max*max + max*max));
      return diameter/2;
    }

    var Star = function() {

      this.orbitRadius = random(maxOrbit(w,h));
      this.radius = random(60, this.orbitRadius) / 12;
      this.orbitX = w / 2;
      this.orbitY = h / 2;
      this.timePassed = random(0, maxStars);
      this.speed = random(this.orbitRadius) / 50000;
      this.alpha = random(2, 10) / 10;

      count++;
      stars[count] = this;
    }

    Star.prototype.draw = function() {
      var x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX,
          y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY,
          twinkle = random(10);

      if (twinkle === 1 && this.alpha > 0) {
        this.alpha -= 0.05;
      } else if (twinkle === 2 && this.alpha < 1) {
        this.alpha += 0.05;
      }

      ctx.globalAlpha = this.alpha;
      ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius);
      this.timePassed += this.speed;
    }

    for (var i = 0; i < maxStars; i++) {
      new Star();
    }

    function animation() {
      ctx.globalCompositeOperation = 'source-over';
      ctx.globalAlpha = 0.8;
      ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 1)';
      ctx.fillRect(0, 0, w, h)

      ctx.globalCompositeOperation = 'lighter';
      for (var i = 1, l = stars.length; i < l; i++) {
        stars[i].draw();
      };

      window.requestAnimationFrame(animation);
    }

    animation();
  }
}
</script>

<style scoped>
body{
  padding: 0;
  margin: 0;
  overflow-y: hidden;
}
.m-trans-all #canvas{
  background-color: #2c343f;
  width: 100%;
  height: 100%;
}
</style>